Small-Signal Stability Analysis Of A Grid Connected Doubly-Fed Induction Generator Under Decoupled P-Q Control

Due to energy shortage and global warming, wind power generation, as a major way to reduce greenhouse gas emissions, is developing fast around the world and the technology has continuously been improved. The doubly-fed induction generator (DFIG) equipped wind turbine (WT) is currently the most popular one due to its capability of allowing direct connection of the stator to AC grid under variable rotor speed as well as for providing decoupled P–Q control capability and offering cost advantages, high energy efficiency, and the fact that the converter rating of appropriately 20%-30% of the total machine power is needed.Small signal stability analysis is conducted considering grid connected DFIG type in this paper. The modeling of a grid connected DFIG system is first set up and research is carried out to argue the stability of the single generator. Different models are formulated and compared with each other for different assumptions (with or without stator transients, with the decoupled P-Q controller or not) by a set of differential algebraic equations (DAE). Then, the mathematical model of rotor-side converter is built with decoupled P-Q control techniques to implement stator active and reactive powers control. Finally, analysis of the oscillation mode and the damping coefficient for the system demonstrate that the grid connected DFIG system with the decoupled P-Q control are stable and indicate that the controller can improve dynamic performance of the DFIG system.